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Haloperidol (Haldol)

First-generation (typical) antipsychotic — high-potency butyrophenone

Mechanism of action

Strongly blocks dopamine D2 receptors in the mesolimbic pathway, reducing positive symptoms of psychosis (hallucinations, delusions, agitation). High potency means heavier extrapyramidal effects than newer agents. Used for acute psychosis, severe agitation/delirium, schizophrenia, Tourette's, and chemotherapy-induced nausea (off-label).

Adverse effects

Life-threatening / NCLEX-tested

Neuroleptic malignant syndrome (NMS) — life-threatening; hyperthermia, severe muscle rigidity, autonomic instability, altered mental status, elevated CK; STOP the drug immediately
Extrapyramidal symptoms (EPS): acute dystonia (early), akathisia, parkinsonism, tardive dyskinesia (late, often irreversible)
QT prolongation → torsades de pointes (especially IV)
Severe hypotension
Lowered seizure threshold
Anticholinergic toxicity (less than low-potency typicals, but real)

Side effects

Common — what to teach

Sedation
Dizziness, orthostatic hypotension
Mild EPS (restlessness, mild stiffness)
Dry mouth, constipation, urinary retention
Hyperprolactinemia (galactorrhea, gynecomastia, menstrual changes)
Weight gain (less than atypicals)

Food & drug interactions

QT-prolonging drugs (ondansetron, methadone, fluoroquinolones, amiodarone, other antipsychotics) compound torsades risk. CNS depressants (alcohol, benzodiazepines, opioids) compound sedation and respiratory depression. Anticholinergics worsen anticholinergic burden. Levodopa/dopamine agonists antagonized — avoid in Parkinson's disease. Lithium plus haloperidol → rare reports of severe encephalopathy.

Nursing implications

Assessment, monitoring, patient teaching

Baseline and periodic ECG (especially IV); monitor QTc — IV haloperidol carries an FDA warning for QT prolongation
Assess for EPS using a structured tool (AIMS for tardive dyskinesia; document at baseline and periodically); have benztropine or diphenhydramine available for acute dystonia (treat IM)
Recognize NMS: hyperthermia + rigidity + autonomic instability + altered mental status — STOP haloperidol, support airway/circulation, dantrolene/bromocriptine per protocol
Monitor BP, HR, temperature, RR, level of consciousness; orthostatic vitals before standing
Avoid in Parkinson's disease (dopamine blockade worsens)
Counsel on the slow onset of antipsychotic benefit (days to weeks for full effect)
Older adults with dementia-related psychosis: increased mortality (boxed warning); short-term use only if behaviorally indicated and after non-pharm strategies

When to hold / contraindications

Suspected NMS (any combination of fever, rigidity, autonomic instability, altered mental status)
QTc > 500 ms or active torsades
Severe hypotension
Parkinson's disease (use a different agent like quetiapine if antipsychotic is needed)
Acute dystonic reaction without provider direction (treat with anticholinergic, then reassess)
Severe CNS depression with potential airway compromise

Memory anchor

Haloperidol = "high potency, high EPS, high QT." Watch for NMS (hot, stiff, altered, autonomic). Have benztropine/diphenhydramine on hand for dystonia.

Reminder: Drug cards are study aids, not clinical guidance. Always cross-check doses, holds, and contraindications with your facility's formulary and your clinical instructors before patient care.

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